@article{21746,
  abstract     = {As vertebrates transitioned from water to land, locomotion shifted from undulatory swimming to limb-based movement. How spinal circuits and their cell types evolved to support this transition remains unclear. We leverage frog metamorphosis, which recapitulates this transition within a single organism, to define how spinal circuits generate aquatic versus terrestrial motor patterns. At swim stages, spinal architecture is uniform, with a transcriptionally and anatomically homogeneous motor and interneurons. As limbs develop and their movement complexifies, spinal circuits expand in neuron number and subtype diversity. This expansion is most pronounced for V1 inhibitory neurons, which increase ∼70-fold and diversify into transcriptionally distinct subtypes. Disrupting transcription factors defining emerging motor and V1 populations reveals molecular segregation between swim and limb circuits, highlighting the role of subtype diversity in motor coordination. A multifold increase in inhibitory neuron diversity thus underlies the tail-to-limb locomotor transition, providing a framework for spinal circuit adaptation during vertebrate evolution.},
  author       = {Vijatovic, David and Toma, Florina Alexandra  and Ignatyev, Y and Harrington, Zoe P and Sommer, Christoph M and Hauschild, Robert and Smits, Matthijs Geert and Dalla Vecchia, Marco and Trevisan, Alexandra J. and Chapman, Phillip and Julseth, Mara and Brenner-Morton, Susan and Gabitto, Mariano I. and Dasen, Jeremy S. and Bikoff, Jay B. and Sweeney, Lora Beatrice Jaeger},
  issn         = {2211-1247},
  journal      = {Cell Reports},
  number       = {4},
  publisher    = {Elsevier},
  title        = {{Multifold increase in spinal inhibitory cell types with emergence of limb movement}},
  doi          = {10.1016/j.celrep.2026.117227},
  volume       = {45},
  year         = {2026},
}

@unpublished{19520,
  abstract     = {Vertebrates exhibit a wide range of motor behaviors, ranging from swimming to complex limb-based movements. Here we take advantage of frog metamorphosis, which captures a swim-to-limb-based movement transformation during the development of a single organism, to explore changes in the underlying spinal circuits. We find that the tadpole spinal cord contains small and largely homogeneous populations of motor neurons (MNs) and V1 interneurons (V1s) at early escape swimming stages. These neuronal populations only modestly increase in number and subtype heterogeneity with the emergence of free swimming. In contrast, during frog metamorphosis and the emergence of limb movement, there is a dramatic expansion of MN and V1 interneuron number and transcriptional heterogeneity, culminating in cohorts of neurons that exhibit striking molecular similarity to mammalian motor circuits. CRISPR/Cas9-mediated gene disruption of the limb MN and V1 determinants FoxP1 and Engrailed-1, respectively, results in severe but selective deficits in tail and limb function. Our work thus demonstrates that neural diversity scales exponentially with increasing behavioral complexity and illustrates striking evolutionary conservation in the molecular organization and function of motor circuits across species.},
  author       = {Vijatovic, David and Toma, Florina Alexandra  and Harrington, Zoe P and Sommer, Christoph M and Hauschild, Robert and Trevisan, Alexandra J. and Chapman, Phillip and Julseth, Mara and Brenner-Morton, Susan and Gabitto, Mariano I. and Dasen, Jeremy S. and Bikoff, Jay B. and Sweeney, Lora Beatrice Jaeger},
  booktitle    = {bioRxiv},
  title        = {{Spinal neuron diversity scales exponentially with swim-to-limb transformation during frog metamorphosis}},
  doi          = {10.1101/2024.09.20.614050},
  year         = {2024},
}